Radio-controlled-clock (RCC) devices that rely on time signal broadcasts have become widely used in recent years. A radio-controlled-clock (RCC) is a timekeeping device that provides the user with accurate timing information that is derived from a received signal, which is broadcast from a central location, to allow multiple users to be aligned or synchronized in time. Colloquially, these are often referred to as “atomic clocks” due to the nature of the source used to derive the timing at the broadcasting side. In the United States, the National Institute of Standards and Technology (NIST) provides such broadcast in the form of a low-frequency (60 kHz) digitally-modulated signal that is transmitted at high power from radio station WWVB in Fort Collins, Colo. The information encoded in this broadcast includes the official time of the United States. This also includes information regarding the timing of the implementation of daylight saving time (DST), which has changed in the United States over the years due to various considerations.
Reception of the time signal, however, is being challenged by a growing number of sources of electromagnetic interference. In particular, the on-frequency interference from the MSF radio station in the United Kingdom has been identified as a particularly challenging jammer for receivers on the East Coast.
This created a need for a new protocol for time signal broadcasts, representing an upgrade to that provided by WWVB that attempts to cost-effectively address the reception challenges. The new protocol should preserve amplitude modulation properties of the legacy time-code broadcast, in order to maintain backwards compatibility and not impact legacy devices, the operation of which should not be affected by the additional features offered by an enhanced protocol.